A. Field of the Invention
The invention concerns a retrofittable intermediate tube for a microscope, especially for a stereomicroscope.
Satisfactory observation with a microscope or stereomicroscope requires that the observer have the pupils of his eyes at the exit pupil of the eyepiece lens used. The optical axis leaving the instrument simultaneously forces a direction of view on him. Thus various observation situations (e. g., object dimensions, adapted equipment, nature of the system, and height of the table on which the microscope is placed) and anatomical details (body dimensions of the observer) lead to constrained sitting positions and body postures which do not always seem desirable from the ergonomic viewpoint. The invention concerns an intermediate tube which allows adjustment of the angle of the tube, relative to the vertical, so that an ergonomic tube adjustment can be found.
B. Description of the Related Art
"Ergotubes" with which the direction of view and/or the height of the eyepiece can be changed are known for microscopes with removable tubes. These ergotubes are generally relatively expensive, and also have the disadvantage that the fixed tube used previously, with its functional elements for producing a real intermediate image (tube lens, deflecting prism, perhaps also a beamsplitter) and for adjustment of the interpupillary distance become superfluous, as the known ergotubes include all those parts. Therefore they are not intermediate units but different and more ergonomic tubes which completely replace the non-ergonomic ones.
On the other hand, German Patent 7931427 (U.S. Pat. No. 4,299,439) describes an intermediate unit which can be inserted between the revolving objective nosepiece and the microscope tube. It can be used with the existing tube and can be used, particularly, to change the eyepiece height. This intermediate unit can be added to existing microscopes. As the goal of the problem on which the German Patent 7931427 (U.S. Pat. No. 4,299,439) was based was to provide an intermediate unit to adjust the eyepiece height, the change of the angle of view remains relatively slight with this known design. This intermediate unit has the disadvantage of requiring, because of its great length, an optical system to form an intermediate image. Aside from the added cost of the lens system, that can also cause vignetting or problems with definition. When this system is used for stereomicroscopes, the cost is obviously doubled because a second supplemental lens system must also be provided for the second beam path.
The voluminous structure and the severely off-centered weight distribution of the parts produce other disadvantages. The experts apparently followed the wrong path in considering the added intermediate image as desirable. The additional real intermediate image required by informed persons can, however, lead disadvantageously to a reduction of the contrast.
Furthermore, the image inversion described as advantageous is technologically superfluous, as most modern microscopes already provide image inversion at other, more suitable locations (e. g., in the binocular tube), so that use of the known intermediate unit returns to an inverted and reversed image.
Another known possibility for changing the eyepiece situation consists of use of a replaceable wedge-shaped intermediate tube unit, which generally contains a prism with two reflective surfaces. Such a system does, to be sure, require only a little mechanical cost, but it has the disadvantage that neither the eyepiece height nor the angle of view can be changed smoothly. The gain in comfort is, again, limited to just a single user or observer situation.
The ergotubes mentioned, as well as the known intermediate unit according to the German Patent 7931427 (U.S. Pat. No. 4,299,439) contain drives which assure that in case of a mechanical alteration of the angle of view by rotating the tube, the beam path is carried around a corresponding angle. Usually one reflecting surface (or more) (deflecting mirror) is tilted about its axis at half the angle through which the beam path is rotated by means of a reduction drive. It is preferred for the axis of rotation for the direction of view (for the tube) to coincide with the axis of rotation of the reflecting surface.
Known solutions for such angle-halving drives are, for example, multistage gear drives with a disadvantageous multiplicity of functional elements, or friction drives, which have a relatively great space requirement because of the necessary axial separation. All these drives have in common the fact that relatively high cost is needed to meet the functional requirements, such as accuracy of the reduction ratio, adequate freedom from play in the bearings, and ability to adjust the optical axis. That necessarily leads to high costs.
The binocular tube attachment described in German 1098233 C2 describes, for instance, a planetary gear drive with bevel gears to control a mirror when the angle of view is changed. Furthermore, a system for adjusting the interpupillary distance is recommended, which also provides for moving a mirror with an angle-halving drive which, in this case, is accomplished as a spatially acting lever drive. This principle is, to be sure, fundamentally suitable for moving a reflecting surface when the angle of view is changed; but the engineering accomplishment is made difficult by the fact that, for this particular application, a considerably larger range is desired for the angle being adjusted. Without additional measures to eliminate errors from play and tolerances in the individual parts, this known solution is therefore inadequate.
Flat lever drives which appear suitable for the invention are also described in German Patent 3117254 and Japanese Patent 4215419. See the contents of the two patents, and especially the corresponding figures with their descriptions. They are considered as disclosed with respect to this application. Cam drives, such as suggested in German Patent 2461044 B2 for a different application, are also conceivable. All these solutions have in common that a mirror can be moved with angular accuracy through the angle .alpha./2 only through precise construction and adjustment of the functional elements. That requires corresponding cost in production, and it is the intent of the invention to improve on that.